Assembly kit having dovetail connection with reduced contact area



Nov. 25. 1969 A. FISCHER 3,479,763

ASSEMBLY KIT HAVING DOVETAIL CONNECTION WITH REDUCED CONTACT AREA FiledNov. 8, 1965 2 Sheets-Sheet 1 Fig. 4

I N VEN TOR.

ARTUR FISCHER BY Nov. 25, 1969 Filed NOV. 3, 1965 A. FISCHER ASSEMBLYKIT HAVING DOVETAIL CONNECTION WITH REDUCED CONTACT AREA 2 Sheets-Sheet2 IN V EN TOR.

ARTUR FISCHER BY United States Patent US. Cl. 4625 7 Claims ABSTRACT OFTIE DISCLOSURE In a toy building kit a socket member has a first exposedsurface which is provided with a groove of undercut configuration havingan outer portion adjacent to the exposed surface and an inner portionbounded by an interior surface and increasing in width in a directioninwardly away from the outer portion. A plug member is provided having asecond exposed surface from which a connecting projection extends whichis adapted to be received in the groove. The projection includes a neckpor tion which is to be received in the outer portion of the groove anda head which is to be slidably received in the inner portion of thegroove and which has a crosssectional area smaller than that of theinner portion so that the projection will be in engagement with theinterior surface only in the region adjacent the outer portion of thegroove.

The present invention relates to an assembly kit. More specifically, theinvention relates to a kit of the type with which various structures canbe assembled from building blocks provided in the kit. Still morespecifically, the invention relates to a kit of the above type in whichthe building blocks are connected together by way of connectingformations respectively provided on the building blocks themselves or inthe form of separate members.

Assembly kits utilizing building blocks of the type mentioned above areknown. There are, for example, disclosed in my copending applicationSer. No. 492,646, filed on Oct. 4, 1965, building blocks from whichmodels and toy structures may be assembled. In such assembly kits thebasic building blocks are provided with grooves which extend inwardly ofone or more exposed faces of the blocks and Whose cross-sectional areaincreases in the direction inwardly away from such exposed faces. Thus,at the surface the area is narrower than inwardly thereof, whereby aslot is defined in the surface. Heads or connecting members of aconfiguration substantially similar to the cross-sectional area of thegrooves are provided on other blocks or in the form of separateconnecting members, and these connecting members or heads are receivablein the grooves. They are joined to necks which are only as wide or justslightly wider than the slots and which extend outwardly through suchslots so as to connect additional elements to the first building block.7

This system of connecting together the blocks has been found to behighly successful since it requires no manipulations, requiring manualdexterity, such as the use of screws which frequently are undesirable,particularly if the kit is to be used by a child. However, it has beenfound that a difiiculty does exist with this system in that themanufacturer is frequently unable to maintain the relatively closetolerances which are required if the connecting means are to be receivedand manipulated with ease within the grooves. This is the caseregardless of whether the blocks and the connecting means are provided,as is preferred, from a plastic or from any other material. If the fitof the connecting means in the grooves is too tight, then adjustment ofthe connecting means relative to the building blocks in which therespective groove 3,479,763 Patented Nov. 25, 1969 is provided, becomestoo difiicult. Conversely, if the fit is too loose, then the connectionis not proper and is likely to come apart. It will be understood that ina construction such as that set forth in the above-mentioned copendingapplication it is desirable that the connections established be firm,but yet that the individual elements, such as blocks and connectingmeans, he movable relative to each other with reasonable ease.

Accordingly, it is a general object of the present invention to overcomethese disadvantages arising from such manufacturing difficulties.

A more specific object of the present invention is to provide aconnecting system as has been outlined above, in which allowance is madefor the almost inevitable tolerance variations which occur duringmanufacturing of building blocks and connecting means, so that tightconnections are achieved with the above system while yet the respectivemembers are movable relative to one another with reasonable case.

In accordance with one feature of my invention I provide, in an assemblykit, a combination of a socket member which has an exposed surfaceprovided with a groove. This groove has a portion adjacent to theexposed surface and increases in width in a direction away from saidsurface. I further provide a plug member having a connecting means,including a connecting portion which slidably extends into the groove soas to at least partially fill the same, and a neck portion on theconnecting portion and received in said portion of the groove. Finally,I provide means for enhancing the flexibility of that part of the socketmember which surrounds the groove so that, upon insertion of theconnecting means into the groove, the surrounding part of the socketmember can yield to pressure exerted by the connecting means.

The novel features which are considered as charac teristic'for theinvention are set forth in particular in the appended claims. Theinvention itself however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings, inwhich,

FIG. 1 is an end view of a building block embodying the invention in oneexample;

FIG. 2 shows a modified embodiment of the invention in a partial endview;

FIG. 3 shows yet a further modification of this invention in a viewsimilar to that of FIG. 2;

FIG. 4 is a top-plan view of a structural member embodying theinvention;

FIG. 5 is an end view, partly in section, of yet a further embodiment ofthe invention;

FIGS. 6-8 show a building block embodying a modification of theinvention in a top-plan view, a side view and a bottom view, and

FIG. 9 shows the components of FIG. 8 separated for clarity ofexplanation.

Turning now to the drawing, and firstly to FIG. 1 thereof, it will beseen that I have provided a building block such as disclosed in myabove-mentioned copending application. This building block is designatedwith reference numeral 1. It is provided with the grooves 2 which arenarrow adjacent the exposed surfaces of the building block and widen intheir cross-sectional area inwardly of these exposed surfaces. One endface of the building block shown in FIG. 1 is provided with acylindrical connecting member or head 3 which is joined to the buildingblock by means of a narrow neck portion 15a (see FIG. 5). The other endface may also be provided with a connecting member or head 3, but Iprefer to provide it instead with crossed grooves 2 (not shown).

In order to enhance the flexibility of that part of the building block,which latter may also be considered a member, which surrounds thegrooves, so that upon insertion of the head 3 into the grooves 2 thesurrounding part of the socket member can yield to the pressure exertedby the head 3, I provide in the embodiment shown in FIG. 1 a slot 4which extends parallel to the respective groove 2 with slight spacingtherefrom. It will be obvious that this will make the lip portions 1a,that is the portions which define the slot leading from the widerportion of the grooves 2 to the exposed surfaces of the socket member 1,more flexible and will enable them to yield to pressure when the heads 3of adjoining building blocks or socket members 1 are inserted into thegrooves 2. Of course, it is possible to use the slots 4 additionally forthe purpose of disposing thin plate-like members therein and therebyconnecting them to the respective socket members 1. Such plate-likemembers may be small pieces of clear plastic which may serve as windowsin a structure built from the present assembly kit.

FIG. 2 shows a modification of the embodiment in FIG. 1. The grooves 2aare not of substantially cylindrical cross section as in FIG. 1, but arerather of the dove-tail type. The resiliency-promoting slots areindicated with reference numeral 4a and extend again parallel to thegrooves 2a; furthermore, they are slanted at the same angle at which therespective side walls of the grooves 2a are slanted.

Turning to FIG. 3, it will be seen that the grooves provided in thesocket member 5 are designated with reference numeral 212 and are ofsubstantially rectangular cross-section. The lip portions, that is theportions which define the area of narrow cross-section adjacent theexposed surface of the socket member 5, are formed by projections 5awhich project from either side of the grooves 2b towards the center, butdo not meet. Again, slots 4 extend parallel to the grooves 2b withslight spacing therefrom. It will be seen that in the embodiments ofFIGS. 2 and 3 such slots extend on either side of grooves 2a and 2b;however, this is of course not necessary and it is possible to provideslots only on one side as is clearly indicated in the embodiment ofFIG. 1. FIG. 4 is a topplan view of the embodiment shown in FIG. 3 andit will be seen from this embodiment that projections 5a are elongated,but are shorter than the grooves 2b. Thus, the projections 5a terminateshort of the respective ends of the grooves 2b by a distance whichcorresponds to the axial length of the head or connecting member 3, sothat in this Way the connecting member 3 may be inserted transversely ofthe axial extension of the grooves 2b if for some reason an axialinsertion is impossible or not desired. The socket member 5 is furtherprovided with a bore, as shown in FIG. 4, which is designated withreference numeral 6 and is preferably centrally located. The bore 6receives an auxiliary rnmeber, such as a cylindrical rod which may serveas an axle, a pivot point or for similar purposes.

The embodiments described with reference to the preceding figures havedealt with providing a firm reception of the connecting member 3 in therespective grooves 2, 2a or 2b. At the same time they have been intendedto prevent binding of this head or connecting member 3 in such grooves.However, to some extent the movement of the head 3 in the respectivegroove will still be relatively stiif and this is as it should be underordinary circumstances, to prevent separation of the members from whicha structure has been built. The exception to this occurs if the kit isto be used by children for whom this stiffness might present certainproblems. To overcome it in such cases, that is to make it still easierto insert the head into the respective groove and to move it therein,there is provided in the embodiment of FIG. 5 an arrangement, wherebythe cross-section of the head will not be entirely complementary to thecross-section of the groove. In other words, the head will be so shapedthat it will engage the surrounding wall of the groove only over part ofits own surface, while the rest is spaced from the wall. At the sametime, some of the tightness which is relinquished by this arrangement,is restored by making the neck 15a just slightly wider than the slotdefined by the lips 12a. This is shown in FIG. 5 where the socket memberis designated with reference numeral 11 and in FIG. 9 where the width aof the neck exceeds the width b of the slot between the lips boundingthe latter. This socket member 11 is provided with a groove 12 similarto the groove 2 shown in the embodiment of FIG. 1. It will beunderstood, of course, that this groove could also have crosssectionsdifferent from the areas shown. At the point at which the groovecommunicates with an exposed surface of member 11, there are providedlips 12a on either side of the slot. These lips are made more elastic bythe provision of at least one additional slot 13 which extends parallelto the groove 12 'as described with reference to the embodiment of FIG.1.

A second socket member or building block 14 is provided with a head orconecting member 15 of complementary-in this case circularcross-sectionwhich is secured to the socket member 14 by means of a narrow neck 15a.The cylindrical connecting member 15 is not quite complementary to thecross-section of the groove 12 so that, when it is received, itslongitudinal axis is slightly offset from the longitudinal axis ofgroove 12 in the direction toward the lips 12a. Thus, the connectingmember 15 will engage the wall surrounding groove 12 only over part ofits surface inwardly adjacent the lips 12a. The neck 15a is slightlywider than the spacing of the lips 12a so that there is a resilientdeflection of the surrounding material of member 11 which is madepossible by provision of the slot 13. It will be understood that thefact that the connecting member 15 does not engage the surrounding wallof groove 12 over its entire surface area, makes it much more easy toinsert and slide the head or connecting member 15 within the groove 12.

At the same time, it will be clear that, if the neck 15a is slightlyshorter than the depth of the lips 12a, as seen looking into the groove12 transversely of its longitudinal axis, when the engagement of thesurface portions of the head 15 with the Wall directly inwardly of thelips 12a will also serve to bias the member on which the head 15 isprovided against the exposed surface of the socket member 11, whichagain assures a tight connection between the members.

The embodiment of FIGS. 68 shows that it is also possible to dispensewith the parallel slot 13 and to provide instead a slot which may beformed at the bottom of groove 12 and extends inwardly toward the centerof the respective member 11. This is also shown in FIG. 9, where thedimension 0 of the neck is slightly shorter than the dimension d. In theembodiment of FIGS. 6-8 the socket member 11 is provided with the usualgrooves 12. one in each longitudinal surface, and is thus divided intofour segments 11a. The provision of the slots 13' at the bottom of therespective grooves 12 imparts increased flexibility to the respectivesegments 11a. The effect is the same as with the provision of thegrooves 13 along and parallel to the grooves 12 as shown in the otherfigures.

The members in accordance with the invention are preferably providedfrom a plastic material, of which polyamide has been foundparticularlysuitable because of its toughness and resiliency. However,other materials may be used.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofassembly kits diifering from the types described above.

While the invention has been illustrated and described as embodied inassembly kits, it is not intended to be limited to the details shown,since various modifications and structural changes may be made withoutdeparting in any way from the spirit of the present invention.

What is claimed as new and desired to be secured by Letters Patent is:

1. In an assembly kit, the combination of a socket member having a firstexposed surface provided with a groove, said groove having an outerportion adjacent to said exposed surface and an inner portion bounded byan interior surface and increasing in width in a direction inwardly awayfrom said first surface and from said outer portion; and a plug memberhaving a second exposed surface provided with a projecting connectingmeans adapted to be received in said groove, said connecting meansincluding a neck portion adapted to be received in said outer portion ofsaid groove and a connecting portion adapted to slidably extend intosaid inner portion of said groove, said neck portion having a lengthwhich is less than the depth of said outer portion of said groove sothat when said connecting means is received in said groove said firstand second surfaces will be biased against one another, and saidconecting portions of said connecting means having a cross-sectionalarea smaller than that of said inner portion of said groove and a heightwhich is smaller than the depth of said inner portion so that when saidconnecting means is received in said groove said connecting portionfrictionally engages said interior surface of said inner portion only inthe region adjacent to said outer portion while being spaced from theremainder of said interior surface of said inner portion, saidconnecting means being operative for firmly connecting said membersagainst separation in a direction transversely of the elongation of saidgroove by the frictional engagement of said members in the regionadjacent to said outer portion of said groove, but for admitting ofsliding displacement of said members relative to one anotherlongitudinally of said groove due to their spacing along said remainderof said interior surface of said inner portion of said groove, with saidfirst and second surfaces remaining in abutment with each other.

2. In an assembly kit as defined in claim 1; said socket member furthercomprising slot means extending adjacent to said groove for enhancingthe flexibility of said socket member in the region of said groove.

3. An assembly kit as defined in claim 2, wherein said slot meansextends laterally of said groove,

4. An assembly kit as defined in claim 2, wherein said slot meansextends parallel to said groove.

5. An assembly kit as defined in claim 2, wherein said slot means isprovided in the bottom of said groove and extends inwardly into thesocket member.

6. An assembly kit as defined in claim 1, 'wherein at least one of saidmembers is made from synthetic plastic material.

7. An assembly kit as defined in claim 1, wherein said neck portion iswider than said outer portion of the groove so that, when saidconnecting means is inserted into said groove, said neck portion willtend to enlarge the cross-sectional area of said outer portion of thegroove.

References Cited UNITED STATES PATENTS 1,092,591 4/1914 Pajeau 46161,863,995 6/1932 Ponstingl 4625 X 1,985,992 1/1935 Hayman 4626 2,493,2851/1950 Granat 63--15.3 2,662,335 12/ 1953 Oalverley 4629 3,032,919 5/1962 Amsler 4626 3,154,281 10/1964 Frank.

FOREIGN PATENTS 240,361 8/ 1962 Australia.

883,574 7/ 1953 Germany.

332,469 11/ 1935 Italy.

586,630 12/1958 Italy.

F. BARRY SHAY, Primary Examiner

